A conventional scanning electron microscope (SEM) is requested for primary use by three Major Users in developing important portions of their ongoing funded research program. All are resident year-round investigators at the Marine Biological Laboratory (MBL) and have made significant preliminary observations using SEM's no longer available to them. There is no permanent SEM at the MBL nor do the Major Users have reasonable access to SEM's elsewhere. Sometimes short-term loans of microscopes to the MBL serve transient summer demands and special purposes, but these arrangements may not be relied on and are not adequate for predictable long-term research efforts. The MBL has an experienced and competent service organization for the maintenance and control of research equipment, including electron beam instruments, and a well-equipped transmission EM facility. The requested SEM would be incorporated into that service structure with special provisions to insure required priority use by the Major Users, while allowing access, as available, to other members of the local research community. The MBL will assume all costs for housing, maintaining, and supervising the SEM, and for providing suitable ancillary equipment.